Hemp is hot. Ever since the 2018 Farm Bill and the federal legalization of hemp and hemp-based products by the FDA slightly over a year ago, the amount of hemp-based products has skyrocketed in the market. Everything from consumables using the flower and seeds, to industrial and consumer products using the hemp bast fiber and hurd, the two constituent parts of the hemp stalk, have become more and more common. There has been an incredible amount of R&D by companies across the US on how we can utilize hemp and make hemp-based products. With roughly 230,000 acres of hemp being planted in 2019, most of it for use in CBD and other less-abundant cannabinoid extraction, the majority of that biomass leftover from the plant is just thrown away. Multiple companies have now started to use this huge amount of hemp biomass for more industrial purposes.
With this wave of hemp-based products sweeping across the US, hemp has begun to be touted as the fix to some of the greatest problems of the 21st century, including improving our health and solving the crisis with non-biodegradable plastics. Although it is very easy to find multiple articles on the health and medicinal properties of cannabinoids and many of the compounds found in the flower of the Cannabis genus, there is undoubtedly a push to make cannabis into some kind of a cure-all for ailments. The push to paint hemp as the savior of our single-use plastics problem that is choking the oceans, clogging the rivers, and languishing in our landfills will only delay taking real actions to mitigate this issue. Hemp bioplastic is a biodegradable polymer that can be made from the cellulose and lipids found in the stalk and seeds of the hemp plant or any species of the Cannabis genus. Multiple companies and organizations are already pursuing ways of breaking down the cellulose found in the plant into sustainable and biodegradable plastic. Yet biodegradable plastics derived from plant cellulose is not a new concept.
These are just some of the many “Anything made from plastic can be made from hemp” memes that can be found shared across all social media platforms by so many.
For decades now the majority of the biodegradable plastics on the market have been made from either corn or soybeans, both of which are some of the most widely grown crops, in the US and globally. Not only this but the US government offers substantial subsidies to corn and soybean growers, not yet for hemp. The nail in the coffin for large scale hemp-based plastics boils down to a lack of processing facilities that can process the hemp. The problem is hemp requires very different techniques for processing and breaking down the hurd to the point it can be utilized in plastics production. Most of the bioplastics like polylactic acid (PLA) are made of corn and soy because currently, production methods are more simple and streamlined, and, due to the subsidies, the cost at which plastic producers can buy corn or soy is even cheaper in many cases than the cost of processing free hemp biomass into PLA. Although hemp has many revolutionary benefits to our society, the myth that it can replace traditional bioplastics is not one of them.
Where hemp and plastic technology realistically merge is the utilization of preexisting polymers and hemp fibers as a strengthing agent. Much like how rebar is used in concrete, when hemp fiber is woven in specific ways, it can act as a strengthening matrix that adds stability to both shear forces and heat mitigation with traditional polymers. Adding fiber to plastics is not a new concept; many industries, from construction to the aerospace industry, have utilized fiber-reinforced polymers in construction. The difference between hemp fiber and traditional fiber reinforced polymers is that hemp fiber is stronger, if processed correctly. Hemp fiber has one of the highest tensile strength-to-weight ratios of any natural plant fiber. When compared to cotton or fiberglass fiber, common fibers used in fiber-reinforced polymers or FRP’s, hemp fiber is far superior. From a 2006 study comparing glass fiber FRP with a hemp FRP, the hemp FRP was about 25% stronger when submitted to load testing and about the same for heat deformation. Planet-3 has even done studies on this and was a part of a 2019 in-depth look into how to produce hemp FRP and how different combinations of fiber added to or detracted from the integral strength of the polymer. Read more about our project and findings here.
We used hemp fiber as a reinforcing agent in molded polymer jars. These jars were a part of our 2019 research into the viability of hemp plastic.
Hemp fiber-reinforced polymers are revolutionary for two main reasons, that the production of hemp-reinforced polymers is not more complicated or advanced than traditional FRP manufacturing methods and that hemp fiber has the potential to be far cheaper and stronger than cotton or glass fibers. Even though we may never see hemp rule the biodegradable plastics market, it very possibly can completely revolutionize smaller, more specialized segments of the plastic industry. As with most things, only time will tell. If the US government decides to subsidize hemp at the same rates it does with other crops like corn and soy, then we may live to see hemp dominate the markets for its cellulose production but given current political sentiment, this is unlikely to happen soon.
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Panthapulakkal S, Sain M. Injection-molded short hemp fiber/glass fiber-reinforced polypropylene hybrid composites—Mechanical, water absorption and thermal properties. Journal of Applied Polymer Science. 2007;103(4):2432-2441. https://onlinelibrary.wiley.com/doi/abs/10.1002/app.25486. Accessed Jan 8, 2020. doi: 10.1002/app.25486.
Barrett A. Hemp plastics. Bioplastics News Web site. https://bioplasticsnews.com/2019/05/04/hemp-plastics/. Updated 2019. Accessed Jan 8, 2020.
Rouse A. Is hemp a plastic pollution solution? . 2018. https://thehempmag.com/2018/02/hemp-plastic-pollution-solution/. Accessed Jan 8, 2020.